The U.S. Supreme Court heard oral arguments Wednesday in a water case that will impact how New Mexico manages water in the Rio Grande.

The case stems from a lawsuit that Texas brought against New Mexico alleging that actions such as groundwater pumping have impacted the amount of water in the Rio Grande that reaches an irrigation district in Texas as well as one in New Mexico—Elephant Butte Irrigation District. The pumping is also impacting deliveries to Mexico. Texas alleged that the level of groundwater pumping in New Mexico led to a violation of the Rio Grande Compact, which governs water use between the states.

However, Texas and New Mexico have reached a proposed settlement known as the consent decree, which is supported by the court-appointed special master. The consent decree outlines how much water New Mexico is entitled to. But the United States intervened in the case and has not agreed to the settlement because, it argues, the agreement would not lead to reduced groundwater pumping. The United States argues that the groundwater pumping is occurring at unsustainable levels and will, eventually, have a devastating impact on the Rio Grande Project and could make it hard for the country to fulfill its treaty obligations with Mexico.

The oral arguments on Wednesday centered around whether states can agree to a new apportionment of water without the federal government’s approval. 

Attorney Jeffrey Wechsler, who represents New Mexico, argued that the United States’ claims should be brought to the federal district court in New Mexico.

Justice Neil Gorsuch expressed some concerns about the federal government’s argument.

“You’re asking us to say the two states cannot resolve their disagreement in this court consistent with a compact so long as the United States objects,” he said. “That’s the upshot of what we’re being asked to enforce.”

Additionally, Gorsuch highlighted that the Rio Grande Compact is an agreement between states. He said the United States’ role is to administer the Rio Grande Project.

Justice Elena Kagan was more sympathetic toward the United States’ arguments.  

“There are compacts that really do involve only the states and don’t have distinctively federal interests attached to them, and this compact is not that,” she said.

She said the Rio Grande Compact is “inextricably intertwined with the Rio Grande Project and the downstream contracts, which, of course, are federal in nature.”

Additionally, Kagan said the United States plays an integral role in the compact’s operation and that breaching the compact would jeopardize the ability to satisfy treaty obligations.

Frederick Liu, an attorney representing the United States, argued that the consent decree imposes additional responsibilities on the federal government and that those obligations are actually contrary to the United States’ contracts with downstream water users.

“A consent decree requires consent. The proposed consent decree in this case, however, would dispose of the United States’ claims without its consent. The decree would impose obligations on the United States without its consent, and the decree would bind the United States to an interpretation of the Rio Grande Compact that is contrary to the Compact itself,” Liu said in his opening argument.

During questioning, Liu argued that the consent decree would require the United States to transfer water at certain times and places.

“And that just flips the (Rio Grande) Project and the Compact on their head because the original design of both was that the determinants of how the allocation works would be the United States and the districts,” he said. “Now what determines the allocation is what the states tell us the allocation should be.” 

Lanora Pettit, an attorney representing Texas, said that the Rio Grande Compact allocates 57 percent of the water to New Mexico and 43 percent to Texas. But, she said, neither the compact nor the downstream contracts specify what the baseline is in determining what constitutes 57 percent. 

“This Court has repeatedly admonished states to figure out such issues amongst themselves,” Pettit argued.

She further said that the consent decree does not violate the Rio Grande Compact and said that it merely tweaks methodology that the United States came up with in the 1970s.